For a portion to enhance the energy efficiency of an air compressor for general industry, an oil injected type and a water injected type that mix oil or water with air sucked inside an air end and compress them together are known.
The oil and the water have effect that they seal narrow clearance via which compression chamber connects with another space and reduce inside leakage and effect that they absorb the heat of compression and prevent the thermic deformation of members of the compressor, reducing compressing power and the energy efficiency is enhanced with both effects.
The oil injected type excels in reliability because it has longtime achievements, however, as it is feared that a component of oil may remain in supplied discharged air though the component of oil is extremely slight, the oil injected type cannot be used for application in which even the existence of a minute oil content is not allowed such as food and a semiconductor. According to the water injected type, supplied air includes no oil content, however, as a countermeasure against rust, corrosion, the failure of lubrication and others is required, the prevalence has retarded, compared with the oil injected type.
However, the development of a water injected air compressor has been recently popular because of a request of a market for clean air that includes no oil content and a screw air compressor is disclosed in Japanese Patent Application Laid-Open Publication No. 2009-180099 which is a first well-known example.
The adoption of a water injected type scroll air compressor is disclosed in Japanese Patent Application Laid-Open Publication No. H8-128395 which is a second well-known example. Besides, results of experiments in which efficiency is enhanced by injecting water into a scroll air compressor are described in “Performance of oil-free scroll-type air compressors” written by T. Yanagisawa, M. Fukuta, and Y. Ogi (Shizuoka University) in Proceedings of International Conference on Compressors and Their Systems as an identification number of IMechE 1999 C542/088, issued in September, 1999 and published by Institution of Mechanical Engineers (IMechE), which is a third well-known example.